Vibrator testing apparatus



Dec. 30, 1952 H. v. ELLIOTT ETAL 2,623,926

VIBRATOR TESTING APPARATUS Original Filed May 15, 1948 INVENTORS HAROLDV. ELLIOTT BROOKS H. SHORT THEIR ATTORNEYS Patented Dec. 30, 1952 UNITEDVIBRATOR TESTING APPARATUS Harold V. Elliott and Brooks H. Short,Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich,a corporation of Delaware Original application May 15, 1948, Serial No.

1949, Serial No. 109,198

2 Claims.

This invention relates to apparatus for converting direct current fromlow voltage to higher voltage and more particularly to the vibratorwhich distributes current in succession to the primary windings of atransformer.

An object of this invention is to provide apparatus which will give avisual indication of the functioning of the vibrator to determinewhether its contacts have been properly adjusted to obtain the requiredcontact separation.

A vibrator which is adapted to be tested by the present apparatus isdescribed and claimed in copending application, Serial No. 27,237, filedMay 15, 1948, of which this application is a division, now Patent No.2,541,223 issued February 13, 1951.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. 1 is an enlarged scale longitudinal sectional view of a vibratorwhich is adapted to be tested by the present apparatus.

Fig. 2 is a sectional view on line 22 of Fig. 1.

Fig. 3 is a reduced scale view of the tool which is used in adjustingthe vibrator contacts.

Fig. 4 is a wiring diagram showing the connections of the vibrator witha current source and primary windings of a transformer.

Fig. 5 is a wiring diagram of the apparatus for determining whether thecontacts have been properly adjusted.

Referring to Figs; 1 and 2 the vibrator comprises a frame 23 whichprovides a magnetic circuit" including a core 2i and pole pieces 22. Thecore 2| extends through a spool which comprises parts 23 and 24 ofmolded insulating material upon which are wound a tape layer 250., acoil 25 of wire and a tape layer 251). An insulating' spacer 25 and theassembly of spool and coil are placed upon the core 2| while the polepieces 22 are spread apart. After making this assembly the parts 22 arebent into parallelism as shown in Fig. 2. One end of the coil 25 marked21 in Fig. 1 is attached to the frame 20 and the other end is connectedto a lead wire 28. The corners of core 2| are deformed to retain thespool.

Screws 3|! secure to the frame 20 a stack of parts comprising aninsulator 3|, metal contact springs 321 and 331 in the same planecarrying respectively contacts 341 and 351 (Figs, 4 and 5),

Divided and this application July 18,

metal contact spring supports in the same plane, an insulator 3|, ametal spacer plate 38, a terminal plate 39, a reed 40, a second terminalplate 39, a second spacer plate 38, a second insulator 3 I, metalcontact spring supports 35 in the same plane, metal contact springs 321and 337 in the same plane and supporting, respectively, contacts 341'and 351 (Figs. 4 and 5), an insulator 3 a metal plate 4 I. All parts ofsaid stack parts are insulated from the screws 3!] by nonconductingsleeves 42 except the plate 4|. Lock washers confined between the headsof the screws 3!] and the plate 4| resist accidental loosening of thescrews. The four insulators 3|, the two spacers 38, the plate 4|, thetwo terminals 39 and the reed each have two holes receiving the bushings42. The contact springs and the contact spring supports each have onehole for receiving a bushing. The grain of the metal of the reed is inthe direction of the longer dimension of the reed.

The contacts 34Z, 35Z, 347, 351 are engageable respectively with movablecontacts 542, Z, 541", 551 each having a spherical face and Welded to arivet 58. Rivets carrying contacts 541 and 551 are attached to resilientcontact supports 511; and the rivets carrying contacts 541 and 551 areattached to resilient contact supports 5T1. Supports 5' and 511" areattached by rivets 58 to the reed 43. An armature 50 is attached to thereed 40 by rivets 6| passing through the armature, the reed and a plate52 against which the rivets are upset.

A wire l0 connects frame 20 with terminal plates 39 and reed 40 andplates 39 are connected by wire H with terminal 12 (Fig. 4). Wire 23(Fig. 4) is connected with blade 331 which carries contact 351" and thisblade is connected by wire 13 with a terminal 14. The blade 321" whichcarries contact 341 is connected by wire 15 with terminal 16. The blade321 which carries contact 342 is connected by wire T1 with a terminal78. The blade 331 which carries contact 351 is connected by wire 13 witha terminal 80.

The vibrator is connected as shown in Fig. 4 with the current source andprimary windings of a transformer. Terminal 72 is connected by wire 93and switch 9| with a storage battery 32 having one terminal grounded.The terminals l4, l5, l8 and are connected respectively with transformerprimary sections 94, 95, 98 and H33 which are grounded at NH. Thetransformer secondary I02 is connected with a rectifier, the outputterminal of which is connected with the apparatus,

such as a high frequency ignition s stem. requiring for its operationrelatively h h voltage direct current. Satisfactory operation of thevibrator is obtained provided the contact closing periods of all of thevibrator contacts are such that ener izaticn of the four sections of theprimary of the transformer are equalized. In order to determ ne whethersuch equalization exists the vibrator is tested by the apparatus shownin Fig. and its relatively fixed contacts are adjusted during the testin order to obtain equalization.

The test apparatus comprises a lever H8 which operates a shaft IIIcarrying switch arms I I2, H3, H4, H5, H6 and III which are connectedrespectively with vibrator side contacts 841, 851, the vibrator coil 25,contacts 35r and 341' and ground. The other end of coil is grounded andthe reed supported contacts are grounded. Switch arm H2 is engageablewith contacts I2I, I22, I23, I24, arm II3 with contacts I8I, I32, I33,I34, arm II4 with contacts I4I, I42, I43, I44, arm II5 with contactsI5I, I52, I53 and I54, arm II6 with contacts I6I, I82, I88 and I64 andarm II! with contacts I'II, I'I2, I13 and III. Contacts I2I, I24, I32and I83 are connected by wire I80 with transformer primary section I8I.Contact I34 is connected by wire I82 with transformer primary sectionI83. Wire I84 connects contacts MI, I42, I43, I44, I53, I54, I5I, I62with transformer primary section I85. Wire I86 connects contact I84 withtransformer primary section I8'I. The primary sections are connectedwith a battery I88 which is grounded. The transformer secondary wiringI99 is connected as shown with a buifer condenser ISI, rectifier tubesI82 and I93, resistances I58, I55 and voltage doubling condensers I98and I9! connected respectively with rectifier output terminals I98 andI99, the former being grounded and the latter being connected withloading resistances 200 and 2III. A cathode ray oscilloscope 2I0 isconnected between wires I88 and I84 in such a manner as to detect thebehavior of the primary sections I8I and I85 and will show on a screenthe traces of wave forms in these primary sections. The traces Aindicate the behavior of one of the sections and the traces B the other.C is the base line on the screen. If the slanting portions or are equalin length to the slantin portions 19, this is an indication that theenergization of the transformer primary section are equal, because theslant portions represent the functioning of the buffer condenser I9I. Iftwo primary sections I8I and I85 are equally energized the buffercondenser will be equally discharged at the time the opposite pairs ofcontacts are closed.

For convenient reference in the description which follows the four pairsof cooperating vibrator contacts are marked I, II, III, IV. To begin thetest the switch handle I I8 is moved from an oil-position into the firstposition shown in Fig. 5 thereby connecting contact pairs I and IIIrespectively with primary sections I85 and I8I. If the wave forms on theoscilloscope screen are not equal, an adjustment of contacts 341 or 341'is made by bending the contact spring supporting plates 38 against whichthe contact supporting spring are biased. It will be observed that eachplate 35 has a relatively narrow neck 3611, the bending of which willdisplace the head 36h of the plate 36 so as to change the normal contactgap. The bending of the neck 381i is effected by the T-shaped tool 220shown in Fig. 3

which includes a handle integral with a shank 22I having a notch 222wide enough to easily receive the neck 3612. By turning the handle theplate 36 can be easily bent in order to change the location of the fixedcontact of a pair relative to the movable contact. The spacing ofcontact pairs I and III is adjusted by means of the tool until the waveform shows equal lengths of slants a and b as shown in Fig. 5. In thesecond operative position of the switch handle IIIJ, contacts III aredropped out and contacts I and IV are connected respectively with theprimary sections I and I 8| The side contact 35Z is adjusted so thatcontacts IV are balanced with contact I. Contacts III and IV are nowbalanced with contacts I and can be used for duplex operation. The thirdoperating position of the switch handle III'I drops contacts I, retainscontacts IV connected with primary section IBI and connects contact IIwith primary section I85. Contacts II are balanced with contacts IV byadjusting the supports 36 which controls the position of contact 351'.All four sets of contacts are now balanced and the vibrator ispresumably properly adjusted. In the fourth position of the switch allfour sets of contacts are connected respectively with the transformerprimary sections for full load operation and both resistances 288 and28I are connected between the rectifier terminals I99 and I98. If thewave forms shown on the oscilloscope screen compares favorably with thewave forms obtained in the other three positions of the switch, theadjustment of the vibrator is satisfactory. If the wave forms obtainedin the fourth position of the switch shows inequality, the test isrepeated and further contact adjustments are made. Generally onerepetition of the test is all that is required to perfeet the adjustmentof the contacts.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollows.

What is claimed is as follows:

1. Apparatus for testing a vibrator having a reed fixed at one end, anarmature supported by the other end of the reed, an electromagnet havinga core offest from the armature and a coil surrounding the core, andfirst, second, third and fourth pairs of contacts, each pair including areed-supported contact and a fixed contact normally separated from thereed-supported contact, the fixed contacts of the first and second pairsbeing at same side of the reed as the magnet core and the fixed contactsof the third and fourth pairs being on the opposite side of the reed, atransformer having its primary winding provided by four primary coilsand having a secondary winding, a buffer condenser and a rectifierconnected with the secondary winding, a loading resistance connectedwith the rectifier, a current source having one terminal connected withone end of each of the primary coils and the other terminal connectedwith the reed and with one end of the magnet coil, a cathode rayoscilloscope connected with the other end each of a certain two of theprimary coils, switches having movable contacts respectively connectedwith the fixed contacts of the four pairs of vibrator contacts and amovable contact connected with that end of the magnet coil remote fromthe end connected with the current source, a manually operable memberfor moving the movable contacts simultaneously into different positions,circuits established by one of the movable contacts in each of itspositions for completing a circuit between the magnet coil and one ofsaid two primary coils whereby the magnet coil is energized to cause thereed to swing in the direction of the fixed contacts of the first andsecond pairs of vibrator contacts, circuits established by two of theother movable switch contacts in the first position of the member forconnecting the fixed contacts of the first and third pairs of vibratorcontacts respectively with those ends of said one of, and of the otherone of said two primary coils remote from the ends connected with thecurrent source, the closing of the first pair of vibrator contactsshort-circuiting the magnet coil so that the reed swings away from themagnet core and effects opening of the short circuit and engagement ofthe third pair of reed contacts, circuits established by another two ofthe movable switch contacts in the second position of the member forconnecting the fixed contacts of the first and fourth pairs of vibratorcontacts respectively with those ends of said one of, and of the otherone of said two primary coils remote from the ends connected with thecurrent source, the closing of the first pair of vibratorshort-circuiting the magnet coil so that the reed swings away from themagnet core and effects opening of the short circuit and engagement ofthe fourth pair of reed contacts, and circuits established by anothertwo of the movable switch contacts in the third position of the memberfor connecting the fixed contacts of the second and fourth pairs ofvibrator contacts respectively with those ends of said one of, and ofthe other one of said two primary coils remote from the ends connectedwith the current source,

the closing of the second pair of vibrator contacts short-circuiting themagnet coil so that the reed swings away from the magnet core andeffects opening of the shortcircuit and engagement of the fourth pair ofvibrator contacts.

2. Apparatus according to claim 1 in which, in the fourth position ofthe manually operable member, circuits are established by said fourswitch movable contacts which are respectively connected with fixedcontacts of the four pairs of vibrator contacts for respectivelyconnecting said fixed vibrator contacts with ends of the four primarycoils remote from those ends connected with the current source andwhich, in the fourth position of the manually operable member, there isanother switch actuated by movement of the member for connecting anotherloading resistance with the rectifier output terminals.

HAROLD V. ELLIOTT. BROOKS H. SHORT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,154,379 Estes Apr. 11, 19392,212,634 Buckingham Aug. 27, 1940 2,470,049 Nulsen May 10, 1949 OTHERREFERENCES Radio-Craft for April 1948, page 56.

The Radio Amateurs Handbook, 1945 edition, published by the AmericanRadio Relay League; pages 185 and 186.

